Re: Dynamic method example in TDPL

[Stanislav Blinov]

 20.08.2010 13:00, Joel Christensen wrote:

There seem to be quite a few errors in this one:

/**
    Date: Aug 20, 2010
    This was copied from TDPL book pages 386 - 387
*/
module dynamicmethods;

import std.stdio;
import std.variant;

alias Variant delegate(Dynamic self, Variant[] args...) DynMethod;

class Dynamic {
    private DynMethod[string] methods;
    void addMethod(string name, DynMethod m) {
        methods[name] = m;
    }
    void removeMethod(string name) {
        methods.remove(name);
    }
    // Dispatch dynamically on method
    Variant call(string methodName, Variant[] args...) {
        return methods[methodName](this, args);
    }
    // Provide syntactic sugar with opDispatch

Variant opDispatch(string m, /*was: Args*/Args...)(/*was: Args args...*/Args args) { // There should've been variadic template instead of variadic function

        Variant[] packedArgs = new Variant[args.length];
        foreach (i, arg; args) {
            packedArgs[i] = Variant(arg);
        }

return call(m, /*was: args*/packedArgs); // args was used instead of packedArgs

    }
}

void main() {
    auto obj = new Dynamic;
    obj.addMethod("sayHello",

delegate Variant(Dynamic, Variant[]...) { // delegate keyword was missing, and it wasn't matching DynMethod signature

            writeln("Hello, world!");
            return Variant();
        });
    obj.sayHello(); // Prints "Hello, world!"
}

Maybe Andrej can add this one to errata too? :)